In various integrated circuits such as processors, workload changes can occur very quickly. As such a dynamic capacitance (Cdyn) also can change quickly, e.g., from very low to very high values in a very few clock cycles. However, a voltage regulator loop, which contains a digital controller and a voltage regulator that provides a regulated voltage to the processor, is much slower to respond and therefore a specified voltage for the device (VID) is set for the worst case current draw, also known as a power virus. Even under the worst case voltage drop, a circuit voltage must not fall below a target value. This circuit voltage is set so that the voltage seen by the circuit is sufficient for error-free operation.
However, setting VID for the worst case current draw implies that in the majority of cases (namely when not running a power virus), the circuit experiences a supply voltage that is greater than required and as such the circuit burns too much power, both as extra leakage and from the extra voltage the circuit switches across.
To aid in power management, an integrated circuit die may include one or more gated power domains for which power may be selectively applied and disrupted, referred to as power gating. Conventionally, power gating is used to intermittently disable or deactivate an entire gated power domain to conserve power when circuitry of the gated power domain is not needed. This may be referred to as placing the gated power domain in a sleep mode or state.
Power gates present an inherent impedance between a power supply and a gated power distribution grid (gated grid). A gated grid voltage may differ from a power supply voltage based on the impedance of the power gates and current consumption of the corresponding gated power domain, in accordance with Ohm's law.
The power supply voltage may be set based on anticipated load conditions. Out of caution, maximum load conditions or maximum current consumption may be assumed. During operation, however, a gated power domain may draw less current from the gated grid than anticipated, and/or the current draw may vary over time. When the gated power domain draws less current than anticipated, the voltage drop over the total load line is less than anticipated. As a result, the gated grid voltage may be higher than a target gated voltage. The higher gated voltage may not necessarily improve performance of the gated power domain, and may decrease power efficiency through increased leakage and/or active power dissipation.